66640 has 60 divisors (see below), whose sum is σ = 190836. Its totient is φ = 21504.

The previous prime is 66629. The next prime is 66643. The reversal of 66640 is 4666.

66640 is nontrivially palindromic in base 13.

It can be written as a sum of positive squares in 2 ways, for example, as 38416 + 28224 = 196^2 + 168^2 .

It is a hoax number, since the sum of its digits (22) coincides with the sum of the digits of its distinct prime factors.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66643) by changing a digit.

66640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3912 + ... + 3928.

2⁶⁶⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95418).

66640 is an abundant number, since it is smaller than the sum of its proper divisors (124196).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66640 is a wasteful number, since it uses less digits than its factorization.

66640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44 (or 31 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 22.

The square root of 66640 is about 258.1472448042. The cubic root of 66640 is about 40.5426061810.

The spelling of 66640 in words is "sixty-six thousand, six hundred forty".